I am contemplating buying this mainly for COD4, have any of you used it and what do you think of it.

Here's a link http://www.splitfish.com/page.cfm?pageid=15

Probably too expensive, but if you want to get closer to PC gaming, I guess that works.

It's awful. If the game is not programed to support KB&M in the first place, it'll take awhile to get used to the sensitivity. Mine had horrible response times in the buttons, some of them got jammed easily and I never got used to aiming with the thing, not to mention the mouse feels like a flimsy toy. The aiming problems where only magnified if the person you're up against is strafing or moving fast. I just went back to the controller and moved on with my life, I've heard some success stories with this thing but the majority of people ends up hating it, just look on their forums.